Damaging air pollutants include sulfur dioxide, particulate matter—a mixture of extremely small particles and water droplets—ozone, and nitrogen dioxide. China accounts for roughly one-third of the global total for these pollutants, according to Krzyzanowski. (See a map of China.)
In neighboring India, air pollution is believed to cause 527,700 fatalities a year. In the United States, premature deaths from toxic air pollutants are estimated at 41,200 annually.
The combustion of fossil fuels—whether to power China's many automobiles, its burgeoning factories, or its expanding megacities—is a primary source of outdoor air pollutants.